Articles have been manufactured in the past from foamed, cross-linked polyolefin wherein such articles were intended for use as shock absorbing, or cushioning members, in a wide variety of applications, including athletic equipment. Such members have been manufactured by others by a process wherein a panel, or sheet-stock, of foamed cross-linked polyolefin (FXLPO), particularly polyethylene, is heated to an elevated temperature and this preheated material then manually positioned within a mold in such manner that a peripheral portion is clamped and sealed in the parting line of complimentary partible mold elements. The material can be further heated and either vacuum molded or compression molded to a preselected shape. It will be appreciated that difficulty is encountered in handling such heated sheet stock because of the tacky, adhesive and cohesive nature of the heated FXLPO material. Quite commonly in manually handling the heated FXLPO panel, portions thereof stick together prior to proper positioning in the mold, hence resulting in a situation where an acceptable product can not be manufactured and material is wasted. Additionally, because cf the clamping of the peripheral boundary of the panel in the mold parting line a great deal of waste flashing is created and must be removed. This, of course, uneconomically increases labor costs and material costs.
The problems noted above are common in forming various pads for sports and athletic equipment such as, for example, hip pads, thigh pads, and knee pads for football equipment. The laterally extending flashing problem in forming such pads is particularly troublesome from a labor and wasted material point of view.
Present hip pad configurations for use with football equipment, generally have substantially raised, somewhat centrally located portions extending outwardly from a base portion. With the above-described manufacturing techniques currently employed, it is expensive to form such raised portions of a material which is not the same as the material of the base portion of the hip pad. That is, because of the difficulty in handling the tacky, hot sheet stock and the problem of accurately manually positioning, and indexing, a different material unto such a tacky material, such pads are unitarily formed from a single piece of sheet stock. It would be desirable to have a process wherein such hip pads could be formed with the raised portion and base portion being of different materials.
In manufacturing thigh pads by the above process there currently is a problem with regard to unacceptable entrapment of air during forming and also difficulty in properly indexing the components used to form these pads. Such thigh pads typically would be formed by first positioning a heated panel of cross-linked, foamed polyolefin in a mold portion, followed by positioning a rigid plastic insert upon the preheated panel. This, in turn, would then be followed by positioning another panel of heated, foamed, cross-linked polyolefin onto the plastic insert in a manner so as to both encapsulate the insert between the two panels, and join the panels at their periphery. The materials would then be peripherally clamped at a mold parting line. This technique, because of the adhesive nature of the heated panels, obviously creates an air entrapment problem if the air is not removed as the laminate is being built up. The removal of such air when handling the sticky, heated panels is indeed, a difficult task. The entrapped air then creates air pockets during molding, resulting in a product which could be unacceptable. Indexing is also quite difficult when one considers the sticky, adhesive and cohesive characteristics of the FXLPO which is being handled. Both of these problems contribute to poor quality, increased labor costs and increased wasted material.
Thus it will be seen that there is a need in the art for providing a process wherein products can be formed without encountering the undesired sticking problem which results when handling heated, foamed, cross-linked polyolefin. A process is also needed wherein the undesired formation of laterally extending flashing during the molding operation is virtually eliminated. A process is also needed wherein laminates can be formed such as, for example, thigh pads without encountering severe air entrapment problems between the various layers.